Three short radius and seven medium radius horizontal wells have beendrilled and completed in thermal steam drive reservoirs at Midway Sunset and Coalinga fields. Cost and production comparisons with vertical wells have shownhorizontal wells to be economically superior. Horizontal wells in low pressure, heavy oil, unconsolidated sand reservoirs create technical completion designchallenges. This paper will present the completion designs for the short andmedium radius horizontal wells, the economic results, the artificial liftdesigns and the current sand control strategy.
The Midway Sunset and Coalinga fields are mature steam drive projects in15°-45° dipping reservoirs. The unconsolidated sands have permeabilities on theorder of 1–3 darcies, oil gravities of 11 to 13 API, and steam chest pressuresof less than 130 psi. The existing vertical well spacing is approximately 3/4acre/well with both line or pattern steam drives. Reservoir simulation studiesshow that horizontal wells will improve sweep efficiency, improve the oil/steamratio, accelerate project life, help control the oil water contact movement, and improve project profitability.
The first three horizontal wells were drilled short radius (143°/100'), beginning in 1990. Short radius wells were initially selected over mediumradius because it allowed the pumps to be placed in the vertical sectionminimizing rod and tubing wear, reduced vertical to horizontal displacement andavoided directional work in the steam chest. The first medium radius well(12°/100') was proposed and drilled in late 1992. The major advantages ofmedium radius wells include significantly longer laterals with improveddirectional control, maximized drawdown with lower pump placement, openholelogging options, larger casing and liner sizes and improved workoveroptions.